Method for extracting lithium from spent batteries

Abstract

Provided in the present application is a method for extracting lithium from spent batteries. The method comprises the following steps: (1) pretreatment, involving: acquiring a spent ternary positive electrode material, and pretreating the spent ternary positive electrode material to obtain black mass; (2) a reduction roasting treatment, involving: subjecting the black mass to reduction roasting to obtain a roasted powder; (3) an acid dissolution treatment, involving: subjecting the roasted powder and a sulfuric acid solution to an acid dissolution reaction to obtain a solid-liquid mixture; and (4) an electrolysis treatment, involving: electrolyzing the solid-liquid mixture, and after electrolysis is finished, filtering same to obtain a filter residue and a lithium-containing solution. By using the method provided in the present application, the recovery rate of lithium is increased to 98% or more.

Description

A method for extracting lithium from waste batteries

[0001] This application claims priority to Chinese Patent Application No. 2024118401679, filed on December 13, 2024, entitled "A Method for Extracting Lithium from Waste Batteries", and Chinese Patent Application No. 2024118401645, filed on December 13, 2024, entitled "A Method for Extracting Lithium from Waste Batteries", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery recycling technology, and in particular to a method for extracting lithium from waste batteries. Background Technology

[0003] With the continuous expansion of the electric vehicle and renewable energy markets, lithium batteries, as an important energy storage device, have been widely used in automobiles, power tools, mobile devices, and other fields due to their high energy density and long lifespan. However, the recycling and disposal of used batteries remains a global challenge. Once batteries are damaged or reach the end of their lifespan, a large number of used batteries are generated, posing potential pollution and resource waste problems to the environment. Among them, lithium batteries using ternary materials as the positive electrode active material are particularly widely used.

[0004] Currently, the main method for recovering valuable metal elements from ternary lithium batteries is the wet process, which involves acid leaching followed by extraction or precipitation. For example, reducing agents and acids can be added to the black powder to completely dissolve it, and the pH of the solution can be adjusted to 1, which requires a large amount of acid. Alternatively, acid and hydrogen peroxide can be used for treatment followed by extraction, which requires a large amount of acid, alkali, and extractant, and the lithium recovery rate is low, only about 92%. Summary of the Invention

[0005] The purpose of this application is to provide a method for extracting lithium from spent batteries, thereby improving the lithium recovery rate and eliminating the need for reducing agents and reducing the use of acid in the acid dissolution process. The specific technical solution is as follows:

[0006] A method for extracting lithium from waste batteries, comprising the following steps:

[0007] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0008] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0009] (3) Acid dissolution treatment: The calcined powder is reacted with sulfuric acid solution to obtain a solid-liquid mixture;

[0010] (4) First electrolysis treatment: The solid-liquid mixture is subjected to first electrolysis. After the first electrolysis is completed, the first filter residue and the first lithium-containing solution are obtained by filtration.

[0011] In some embodiments of this application, the method for extracting lithium includes the following steps:

[0012] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0013] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0014] (3) Acid dissolution treatment: The calcined powder is subjected to acid dissolution reaction with sulfuric acid solution to obtain a solid-liquid mixture; the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3);

[0015] (4) Electrolysis treatment: The solid-liquid mixture is electrolyzed. After the electrolysis is completed, the mixture is filtered to obtain filter residue and lithium-containing solution. The electrolysis is the first electrolysis, the filter residue is the first filter residue, and the lithium-containing solution is the first lithium-containing solution.

[0016] In some embodiments of this application, step (2), the reduction calcination of the black powder, includes:

[0017] The black powder is calcined in the presence of a reducing agent, which includes C and / or CO; and in step (2), the calcined powder obtained includes Li2CO3 and Me-containing powder; wherein the Me-containing powder includes elemental Me and / or MeO; and the Me is selected from at least one of Ni, Co, and Mn elements.

[0018] In some embodiments of this application, in step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(1.01~1.1).

[0019] In some embodiments of this application, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase, wherein the liquid phase contains Li2SO4 and MeSO4, and the solid phase contains Li2CO3 and Me-containing powder.

[0020] In some embodiments of this application, in step (3), in the liquid phase, the molar amount of Li in Li2SO4 is p1, and the molar amount of Me in MeSO4 is p2, satisfying p1 > p2; in the solid phase, the molar amount of Me in the Me-containing powder is p3, and the molar amount of Li in Li2CO3 is p4, satisfying p3 > p4.

[0021] In some embodiments of this application, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%.

[0022] In some embodiments of this application, step (4) of electrolyzing the solid-liquid mixture includes electrolyzing the MeSO4 in the liquid phase of the solid-liquid mixture.

[0023] In some embodiments of this application, in step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, when the electrolysis capacity C1 in the electrolysis process satisfies Equation 1, the electrolysis ends; 10Ah≤C1 Equation 1.

[0024] In some embodiments of this application, in step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, the first lithium elution rate after the acid dissolution treatment in step (3) is 88% to 90%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-a; 11Ah≤C1≤13Ah Formula 1-a.

[0025] In some embodiments of this application, in step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, the first lithium elution rate after the acid dissolution treatment in step (3) is 90% to 92%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-b; 10Ah≤C1≤12Ah Formula 1-b.

[0026] In some embodiments of this application, in step (4), the lithium-containing solution includes Li2SO4; in the lithium-containing solution, the mass of the Li2SO4 is n1, satisfying n1 > m1, where m1 is the mass of the Li2SO4 in the liquid phase of the solid-liquid mixture in step (3).

[0027] In some embodiments of this application, in step (4), the second lithium elution rate of the lithium-containing solution is ≥98%.

[0028] In some embodiments of this application, in step (4), the filter residue includes the Me-containing powder; the mass percentage of the Me-containing powder in the filter residue is w1%; satisfying: w1% > w2%; wherein w2% is the mass percentage of the Me-containing powder in the solid phase in the solid-liquid mixture in step (3).

[0029] In some embodiments of this application, in step (4), the electrolysis further yields an anode product and a cathode product; the anode product includes MnO2; the cathode product includes at least one of elemental Ni and elemental Co.

[0030] In some embodiments of this application, at least one of the following conditions is met:

[0031] Condition a: In step (2), the amount of the reducing substance used is 8 wt% to 15 wt% of the black powder;

[0032] Condition b: In step (2), the reduction calcination temperature T3 is 550℃~700℃, and the calcination time t3 is 1h~3h;

[0033] Condition c: In step (3), the concentration of the sulfuric acid solution is 1 mol / L to 5 mol / L;

[0034] Condition d: In step (4), the voltage U1 of the electrolysis is 2.5V to 4.5V and the temperature T1 is 30℃ to 80℃.

[0035] This application provides a method for extracting lithium from waste batteries. The method first involves roasting the black powder from the waste batteries with a reducing agent, then performing acid dissolution treatment by controlling the amount of acid, and finally electrolytically leaching the lithium into the liquid phase. This process removes most of the nickel, cobalt, and manganese in powder form, improving the lithium elution rate (i.e., lithium recovery rate) and yielding high-purity nickel, cobalt, and manganese powder. Specifically, the reduced nickel, cobalt, and manganese become elemental and / or metal oxides, while lithium becomes solid Li₂CO₃. Controlling the amount of acid used in the acid dissolution treatment reduces the amount of acid required and eliminates the need for a reducing agent. Electrolysis then uses the acid generated to dissolve the undissolved solid Li₂CO₃ from the acid dissolution process, further improving the lithium elution rate. The resulting solid powder contains no lithium, and no additional acid is consumed during the electrolysis process. Furthermore, the method only requires crushing the cathode material of the waste ternary lithium batteries and then removing the binder and electrolyte at high temperature. The carbon powder is removed during the reduction and combustion process, reducing energy consumption. Using the method provided in this application to extract lithium from waste batteries, the lithium elution rate can reach over 98%. Of course, implementing any product or method of this application does not necessarily require achieving all the advantages described above simultaneously.

[0036] In some embodiments of this application, the method for extracting lithium includes the following steps:

[0037] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0038] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0039] (3) Acid dissolution treatment: The calcined powder is subjected to acid dissolution reaction with sulfuric acid solution to obtain a solid-liquid mixture;

[0040] (4) First electrolysis treatment: The solid-liquid mixture is subjected to a first electrolysis. After the first electrolysis is completed, the mixture is filtered to obtain a first filter residue and a first lithium-containing solution.

[0041] (5) Purification treatment: The first lithium-containing solution is purified to obtain purified Li2SO4.

[0042] In some embodiments of this application, in step (5), the purification process is selected from any of the following:

[0043] Method 1: The purification process is a second electrolytic process, which includes the following steps:

[0044] The calcined powder is added to the first lithium-containing solution to obtain a slurry. The slurry is then subjected to a second electrolysis. After the second electrolysis is completed, the slurry is filtered to obtain a second filter residue and a second lithium-containing solution. The second lithium-containing solution contains the purified Li2SO4. The slurry contains a solid phase and a liquid phase.

[0045] Method 2: Organic solvent extraction;

[0046] Method 3: Add alkali to precipitate.

[0047] In some embodiments of this application, step (5) is the first method, wherein the solid content of the slurry is 1 g / L to 100 g / L; preferably, the solid content of the slurry is 5 g / L to 80 g / L.

[0048] In some embodiments of this application, step (5) is the first method, wherein the liquid phase of the slurry contains Li2SO4 and MeSO4, and the solid phase contains the calcined powder.

[0049] In some embodiments of this application, step (5) is the first method, and the conditions for the end of the second electrolysis include: for every 100g of the black powder, when the electrolysis capacity C2 in the second electrolysis process satisfies formula a, the second electrolysis ends;

[0050] Wherein, C1 is the electrolytic capacity for every 100g of the black powder during the first electrolysis process; the value range of C1 is: 10Ah≤C1, and more preferably, the value range of C1 is: 10Ah≤C1≤13Ah.

[0051] In some embodiments of this application, step (5) is the first method, the second lithium-containing solution includes Li2SO4, and the mass of Li2SO4 in the second lithium-containing solution is s1; in step (4), the first lithium-containing solution includes Li2SO4 and MeSO4, and the mass of Li2SO4 in the first lithium-containing solution is n1; satisfying s1>n1>m1, where m1 is the mass of Li2SO4 in the liquid phase of the solid-liquid mixture in step (3).

[0052] In some embodiments of this application, step (2), the reduction calcination of the black powder, includes:

[0053] The black powder is calcined in the presence of a reducing agent, which includes C and / or CO; and in step (2), the calcined powder obtained includes Li2CO3 and Me-containing powder; wherein the Me-containing powder includes elemental Me and / or MeO; and the Me is selected from at least one of Ni, Co, and Mn elements.

[0054] In some embodiments of this application, in step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3); preferably, the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(1.01~1.1).

[0055] In some embodiments of this application, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase, wherein the liquid phase contains Li2SO4 and MeSO4, and the solid phase contains Li2CO3 and Me-containing powder.

[0056] In some embodiments of this application, in step (3), the molar amount of Li in Li2SO4 is p1 and the molar amount of Me in MeSO4 is p2, satisfying p1 > p2.

[0057] In the solid phase, the molar amount of Me element in the Me-containing powder is p3, and the molar amount of Li element in Li2CO3 is p4, satisfying p3 > p4.

[0058] In some embodiments of this application, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%.

[0059] In some embodiments of this application, step (4) of performing a first electrolysis of the solid-liquid mixture includes electrolyzing the MeSO4 in the liquid phase of the solid-liquid mixture.

[0060] In some embodiments of this application, in step (4), the conditions for the termination of the first electrolysis include: for every 100g of the black powder, the first electrolysis terminates when C1 satisfies formula b; 10Ah≤C1≤13Ah Formula b.

[0061] In some embodiments of this application, in step (4), the second lithium elution rate of the first lithium-containing solution is ≥98%.

[0062] In some embodiments of this application, in step (4), the first filter residue includes the Me-containing powder, wherein the mass percentage of the Me-containing powder in the first filter residue is w1%; satisfying w1% > w2%, wherein w2% is the mass percentage of the Me-containing powder in the solid phase in the solid-liquid mixture of step (3).

[0063] In some embodiments of this application, in steps (4) and (5), the first electrolysis process further yields a first anode product and a first cathode product, and the second electrolysis process further yields a second anode product and a second cathode product; the first anode product and the second anode product each independently include MnO2; the first cathode product and the second cathode product each independently include at least one of elemental Ni and elemental Co.

[0064] In some embodiments of this application, at least one of the following conditions is met:

[0065] Condition a: In step (2), the amount of the reducing substance used is 8 wt% to 15 wt% of the black powder;

[0066] Condition b: In step (2), the reduction calcination temperature T3 is 550℃~700℃, and the calcination time t3 is 1h~3h;

[0067] Condition c: In step (3), the concentration of the sulfuric acid solution is 1 mol / L to 5 mol / L;

[0068] Condition d: In step (4), the voltage U1 of the first electrolysis is 2.5V to 4.5V and the temperature T1 is 30℃ to 80℃;

[0069] Condition e: In step (5), the voltage U2 of the second electrolysis is 2.5V to 4.5V and the temperature T2 is 30℃ to 80℃.

[0070] In some embodiments of this application, the purity of the Li2SO4 obtained after purification is ≥99%.

[0071] The method for extracting lithium from waste batteries provided in this application not only improves the lithium elution recovery rate but also increases the purity of the product Li₂SO₄. Specifically, black powder is reduced and roasted with a reducing agent to obtain a roasted powder containing lithium carbonate and nickel, cobalt, and manganese. Lithium is extracted by electrolysis of the reduced-roasted powder. After dissolving the roasted powder with a slight excess of acid, the dissolved nickel sulfate, cobalt sulfate, and manganese sulfate are subjected to a first electrolytic treatment. The acid generated from the first electrolytic treatment dissolves undissolved lithium carbonate in the solid phase, improving the lithium elution rate and obtaining a solid powder and a first lithium-containing solution. The lithium elution rate of the first lithium-containing solution is ≥98%, and the first lithium-containing solution contains Li₂SO₄ and trace amounts of MeSO₄. The first lithium-containing solution is then subjected to a second electrolytic treatment to further purify lithium. Alternatively, further purification of lithium can be achieved through organic solvent extraction or alkali precipitation. The second electrolytic treatment can be achieved by adjusting the solid content of the slurry using the calcined powder after calcination, so that the electrolysis can be carried out completely. The second electrolytic treatment yields a small amount of nickel-cobalt metal and manganese dioxide, and a purified lithium sulfate solution with a purity of over 99%.

[0072] Furthermore, the amount of sulfuric acid used in this method is significantly reduced compared to traditional processes, which often require SO4 in combination with Li, Co, Ni, and Mn. 2- If calculated using sulfur (S), 1 mol Li corresponds to 0.5 mol S, and 1 mol Co / Ni / Mn corresponds to 1 mol S. Therefore, the required amount of S moles needs to match the molar amounts of Li, Co, Ni, and Mn. However, in this method, the H₂SO₄ produced during the electrolysis of CoSO₄, NiSO₄, and MnSO₄ reacts with the undissolved Li. Therefore, only the amount of SO₄ needed to produce the required amount of Li is required overall. 2- Therefore, in this process, a slight excess of sulfuric acid is used, for example, the molar ratio of Li to H is 1:(1.01~1.1), which can be used to acid dissolve the calcined powder, reducing the need for sulfuric acid or acidic substances and reducing agents, and the lithium elution rate is high.

[0073] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0074] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0075] Figure 1 is an experimental flowchart of Embodiment 1-1 of this application;

[0076] Figure 2 is an experimental flowchart of Embodiment 2-1 of this application. Detailed Implementation

[0077] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0078] Currently, the main method for recycling valuable metal elements from ternary lithium batteries is the wet process, which requires the use of large amounts of acids, alkalis, and extractants, and results in a low lithium recovery rate. Therefore, this application provides a method for extracting lithium from spent batteries to improve the lithium recovery rate, and eliminates the need for reducing agents and reduces acid usage during the acid dissolution process.

[0079] This application provides a method for extracting lithium from waste batteries, which includes the following steps:

[0080] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0081] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0082] (3) Acid dissolution treatment: The calcined powder is reacted with sulfuric acid solution to obtain a solid-liquid mixture;

[0083] (4) Electrolysis treatment: The solid-liquid mixture is electrolyzed. After the electrolysis is completed, the residue and lithium-containing solution are obtained by filtration.

[0084] In some embodiments of this application, in step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3).

[0085] This application also provides a method for extracting lithium from waste batteries, which includes the following steps:

[0086] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0087] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0088] (3) Acid dissolution treatment: The calcined powder is subjected to acid dissolution reaction with sulfuric acid solution to obtain a solid-liquid mixture; the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3); wherein, the electrolysis is the first electrolysis, the filter residue is the first filter residue, and the lithium-containing solution is the first lithium-containing solution;

[0089] (4) Electrolysis treatment: The solid-liquid mixture is electrolyzed. After the electrolysis is completed, the residue and lithium-containing solution are obtained by filtration.

[0090] In this application, ternary cathode material refers to ternary cathode material mainly composed of LiMeO2, wherein Me is selected from at least one of the elements Ni, Co, and Mn.

[0091] The method provided in this application involves calcining black powder with a reducing agent to convert the Me element in the black powder into elemental Me and / or MeO, and the lithium element into solid Li2CO3. A slightly excess of acid is used to dissolve the calcined black powder. During the acid dissolution process, sulfuric acid converts most of the Li2CO3 into the more soluble Li2SO4. Inevitably, a small amount of Me and / or MeO is also dissolved into MeSO4. The dissolved MeSO4, such as nickel sulfate, cobalt sulfate, or manganese sulfate, is then electrolyzed. The acid generated by the electrolysis is used to dissolve the small amount of undissolved solid Li2CO3, improving the lithium elution rate and obtaining a solid powder and a lithium-containing solution. The lithium elution rate of the lithium-containing solution is ≥98%.

[0092] The method provided in this application significantly reduces the amount of sulfuric acid used compared to traditional processes, which typically require SO4 in combination with Li, Co, Ni, and Mn. 2- If calculated using sulfur (S), 1 mol Li corresponds to 0.5 mol S, and 1 mol Co / Ni / Mn corresponds to 1 mol S. Therefore, the required amount of S moles needs to match the molar amounts of Li, Co, Ni, and Mn. However, in this method, the H₂SO₄ produced during the electrolysis of CoSO₄, NiSO₄, and MnSO₄ can react with the undissolved Li. Therefore, only the amount of SO₄ needed to produce the Li is required. 2- In this process, the molar ratio of Li in the calcined powder to H in the sulfuric acid solution is 1:(0.98~1.3), which reduces the need for sulfuric acid or acidic substances and reducing agents, and also results in a high lithium elution rate.

[0093] Specifically, in the method provided in this application, the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3), preferably 1:(1.01~1.1). For example, the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution can be 1:0.98, 1:1.01, 1:1.02, 1:1.04, 1:1.07, 1:1.08, 1:1.1, 1:1.17, 1:1.25, or 1:1.3, or any two of the above numbers. By controlling the amount of sulfuric acid within the above range, most of the Li2CO3 in the calcined powder can be dissolved to generate Li2SO4. Li2SO4 enters the liquid phase of the solid-liquid mixture. At the same time, a small amount of elemental Me and / or MeO in the calcined powder will also react with sulfuric acid to generate MeSO4, which also enters the liquid phase of the solid-liquid mixture. Acid dissolution yields a large amount of Li₂SO₄, a small amount of undissolved solid Li₂CO₃, a large amount of undissolved solid elemental Me and / or MeO, and a small amount of MeSO₄. The large amount of Li₂SO₄ and the small amount of MeSO₄ enter the liquid phase, while the small amount of undissolved solid Li₂CO₃ and the large amount of undissolved solid elemental Me and / or MeO remain in the solid phase. Through acid dissolution, not only can most of the Li₂SO₄ be dissolved... + The Li enters the liquid phase, while most of the Me-containing powder remains in the solid phase. + Separating Me-containing powders using both liquid and solid phases can yield high-purity Me-containing powders. These powders primarily include Ni, Co, and MnO, and Li... + It has a high elution rate in the liquid phase (around 88% to 92%) and fewer impurity phases in the liquid phase.

[0094] In this process, by reasonably controlling H + The amount or SO4 2- The amount of H + The amount of Li + A slight excess of the solution allows for the "stepwise" elution of Li. The first step involves acid washing (H+). + Most of the Li element was eluted from the solid phase and impregnated into the liquid phase. At the same time, the Me element also combined with some SO4. 2- Immersed in the liquid phase, controlling the portion of SO4 bound by Me element. 2-The molar amount of the first step corresponds to the amount of uneluted Li₂CO₃ in the solid phase, preparing for the second step of lithium electrolysis. The second step utilizes the electrolysis of MeSO₄ in the liquid phase to generate H₂SO₄. Since the amount of H₂SO₄ generated corresponds to the amount of uneluted Li₂CO₃ in the solid phase, it allows for the elution of as much Li₂CO₃ as possible from the remaining solid phase, while the Me element remains in the solid phase, i.e., the filter residue. This two-step elution process avoids acid waste and achieves a high overall elution rate (over 98%), while the Me element remains in the solid phase, thus achieving the separation of Li and Me elements.

[0095] If H + Excessive amounts will wash away more elemental Me and / or MeO, reducing the amount of Ni in the liquid phase. 2+ Co 2+ Increased content of certain elements affects the purity of Li₂SO₄, increasing the complexity of subsequent purification and also impacting the recovery rates of nickel, cobalt, and manganese. If H₂... + Too little, Li + The elution rate is low, which is not conducive to lithium recovery, and the Li in the Me-containing powder is also low. + The content will increase, but the purity will be lower, requiring further purification.

[0096] When the molar ratio of Li in the calcined powder to H in the sulfuric acid solution is 1:(1.01~1.1) during acid dissolution, the lithium elution rate is between 88% and 92%, indicating that proper adjustment of the Li content is crucial. + With H + The molar ratio, even if H + A slight excess can make Li + This allows for more thorough separation of Me-containing powders in both liquid and solid phases, further improving the purity of nickel-cobalt-manganese powders, primarily including Ni, Co, and MnO, and Li. + It has a higher elution rate in the liquid phase and fewer impurity phases in the liquid phase.

[0097] In this application, the first lithium elution rate after acid dissolution treatment is 88%–92%. Controlling this range not only achieves a high overall lithium elution rate but also improves the recovery rate and purity of Me. If the first lithium elution rate is too high, more acid will be used, resulting in more Me being eluted, wasting acid and reducing Me recovery, thus affecting Li₂SO₄ purity. If the first lithium elution rate is too low, more Li will remain in the solid phase, hindering Li recovery and reducing solid phase purity.

[0098] In this application, the concentration of sulfuric acid is not strictly required. The concentration of the sulfuric acid solution can be selected from 1 mol / L to 5 mol / L, and further selected from 4.5 mol / L to 5.0 mol / L. For example, when using high-concentration sulfuric acid, such as greater than 5 mol / L, the concentration of sulfuric acid can be diluted with water to make the acid dissolution process easier; or sulfuric acid with a concentration of 1 mol / L to 5 mol / L can be used directly. Selecting sulfuric acid in this concentration range is beneficial to completing the acid dissolution process in a short time, and the acid dissolution reaction will also be more thorough. In some embodiments of this application, in step (2), the reduction roasting of the black powder includes: roasting the black powder in the presence of a reducing substance, the reducing substance including C and / or CO; and, in step (2), the roasted powder obtained includes Li2CO3 and Me-containing powder; wherein, the Me-containing powder includes elemental Me and / or MeO; Me is selected from at least one of Ni, Co, and Mn elements.

[0099] In some embodiments of this application, in step (2), the amount of reducing agent is 8 wt% to 15 wt% of the black powder; the reduction roasting temperature T3 is 550℃ to 700℃, and the roasting time t3 is 1h to 3h. For example, the amount of reducing agent can be 8 wt%, 10 wt%, 12 wt%, 13 wt%, or 15 wt% of the black powder, or any two of the above figures; the reduction roasting temperature T3 can be 550℃, 580℃, 620℃, 650℃, or 700℃, or any two of the above figures; the roasting time t3 can be 1h, 1.5h, 2h, 2.5h, or 3h, or any two of the above figures. By controlling the amount of reducing agent and the reduction roasting temperature and reaction time within the above ranges, the black powder can fully react with the reducing agent, converting the lithium element in the black powder into Li2CO3, and the Me element in the black powder into elemental Me and / or MeO, which is beneficial for subsequent acid dissolution treatment.

[0100] For example, when the reducing substance used in step (2) is C, the reaction equation is: 2LiMeO2+C=Li2CO3+Me+MeO.

[0101] When using carbon powder for reduction, an inert gas, such as N2, can be introduced.

[0102] For example, when the reducing substance used in step (2) is CO, the reaction equation is: 2LiMeO2+2CO=Li2CO3+Me+MeO+CO2.

[0103] In some embodiments of this application, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase. The liquid phase contains Li₂SO₄ and MeSO₄, and the solid phase contains Li₂CO₃ and Me-containing powder. In some embodiments of this application, in step (3), in the liquid phase, the molar amount of Li in Li₂SO₄ is p1, and the molar amount of Me in MeSO₄ is p2, satisfying p1 > p2; in the solid phase, the molar amount of Me in the Me-containing powder is p3, and the molar amount of Li in Li₂CO₃ is p4, satisfying p3 > p4. The black powder mainly contains LiMeO₂, and the molar ratio of Li to Me is approximately 1:1. The ratio of the two remains unchanged in the calcined powder obtained after calcination. Sulfuric acid preferentially reacts with Li2CO3 in the calcined powder, and then with elemental Me and / or MeO in the calcined powder. Therefore, most of the Li2CO3 reacts with sulfuric acid to form Li2SO4, while a small amount of elemental Me and / or MeO also reacts with sulfuric acid to form MeSO4. A large amount of Li2SO4 and a small amount of MeSO4 enter the liquid phase, so p1 > p2 in the liquid phase. A small amount of undissolved solid Li2CO3 and a large amount of undissolved solid elemental Me and / or MeO remain in the solid phase, so p3 > p4 in the solid phase.

[0104] In some embodiments of this application, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%. After acid dissolution treatment, most of the Li2CO3 in the calcined powder reacts with sulfuric acid to generate Li2SO4. The generated Li2SO4 enters the liquid phase, that is, most of the lithium element in the calcined powder enters the liquid phase. The first lithium elution rate after acid dissolution treatment is 88% to 92%.

[0105] In this application, the acid dissolution treatment in step (3) includes the following reactions: Li2CO3+H2SO4=Li2SO4+CO2↑+H2O; Me+H2SO4=H2↑+MeSO4; MeO+H2SO4=H2O+MeSO4.

[0106] In some embodiments of this application, step (4) of electrolyzing the solid-liquid mixture includes electrolyzing MeSO4 in the liquid phase of the solid-liquid mixture. In some embodiments of this application, in step (4), the lithium-containing solution includes Li2SO4; in the lithium-containing solution, the mass of Li2SO4 is n1, satisfying n1 > m1, where m1 is the mass of Li2SO4 in the liquid phase of the solid-liquid mixture in step (3). After electrolysis, Li2CO3 in the solid phase will also leach out in the form of Li2SO4. In some embodiments of this application, in step (4), the second lithium elution rate of the lithium-containing solution is ≥98%.

[0107] In this application, when Me is selected from Ni, Co, and Mn (i.e., nickel-cobalt-manganese ternary batteries), the electrolysis of CoSO4 yields products including elemental Co and sulfuric acid; the electrolysis of NiSO4 yields products including elemental Ni and sulfuric acid; and the electrolysis of MnSO4 yields products including sulfuric acid containing MnO2. The proportions of nickel, cobalt, and manganese in MeSO4 are not limited in this application, but are generally similar to the proportions of nickel, cobalt, and manganese in the positive electrode active material. Exemplarily, the electrolysis reaction is carried out in the following manner:

[0108] The electrolytic treatment in step (4) includes the following reactions:

[0109]

[0110] Electrolysis of MeSO4 in the solid-liquid mixture produces sulfuric acid, allowing the remaining small amount of solid phase Li2CO3 to continue reacting with sulfuric acid to form Li2SO4 that can exist in the liquid phase. Therefore, the mass n1 of Li2SO4 in the lithium-containing solution is greater than the mass m1 of Li2SO4 in the liquid phase of the solid-liquid mixture in step (3), thus improving the lithium elution rate. The second lithium elution rate of the lithium-containing solution is ≥98%. This means maximizing the elution rate of Li... + In the liquid phase, nickel, cobalt, and manganese are separated in the solid phase, thus achieving the separation and purification of the two elements, namely Li and Me, where Me is Ni, Co, and Mn.

[0111] In some embodiments of this application, in step (4), the filter residue includes Me-containing powder; the mass percentage of Me-containing powder in the filter residue is w1%; satisfying: w1% > w2%; where w2% is the mass percentage of Me-containing powder in the solid phase of the solid-liquid mixture in step (3). In the above electrolytic treatment, since the Li2CO3 acid in the solid phase dissolves and immerses in the liquid phase, it is equivalent to purifying the solid phase. Therefore, the mass percentage of Me-containing powder in the filter residue w1% is greater than the mass percentage of Me-containing powder in the solid phase of the solid-liquid mixture in step (3) w2%. That is, the sulfuric acid generated by the first electrolysis can react with Li2CO3 in the solid phase, which is equivalent to purifying the solid phase. Therefore, the mass percentage of Me-containing powder in the first filter residue increases.

[0112] In some embodiments of this application, in step (4), electrolysis also yields an anode product and a cathode product; the anode product includes MnO2; the cathode product includes at least one of elemental Ni and elemental Co. Taking a nickel-cobalt-manganese ternary battery as an example, the above electrolysis yields the anode product MnO2 and the cathode products elemental Ni and elemental Co.

[0113] In some embodiments of this application, the conditions for ending electrolysis in step (4) include: for every 100g of black powder, when the electrolysis capacity C1 in the electrolysis process satisfies Equation 1, the electrolysis ends; 10Ah≤C1 Equation 1.

[0114] By adjusting the electrolysis capacity C1 within the above range, the electrolysis of MeSO4 is achieved, thereby separating the original compounds with MeSO4. 2+ Combined SO4 2- , with Li + This combination improves the elution rate of lithium.

[0115] In some embodiments of this application, the conditions for ending electrolysis in step (4) include: for every 100g of the black powder, the first lithium elution rate after acid dissolution treatment in step (3) is 88% to 90%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-a; 11Ah≤C1≤13Ah Formula 1-a.

[0116] In some embodiments of this application, the conditions for ending electrolysis in step (4) include: for every 100g of the black powder, the first lithium elution rate after acid dissolution treatment in step (3) is 90% to 92%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-b; 10Ah≤C1≤12Ah Formula 1-b.

[0117] The Li elution rate during the acid dissolution process is related to the electrolytic capacity C1 of the subsequent electrolysis. In this application, the electrolytic capacity C1 during the electrolysis process can be determined based on the first Li elution rate during the acid dissolution process. For example, when the first lithium elution rate after acid dissolution is high, at 90% to 92%, the MeSO4 content in the liquid phase is low, and the electrolytic capacity C1 required for electrolysis is also low, satisfying Equation 1-b: 10Ah≤C1≤12Ah; when the first lithium elution rate after acid dissolution is low, at 88% to 90%, the MeSO4 content in the liquid phase is high, and the electrolytic capacity C1 required for electrolysis is also high, satisfying Equation 1-a: 11Ah≤C1≤13Ah.

[0118] In some embodiments of this application, the electrolysis voltage U1 is 2.5V to 4.5V, and the temperature T1 is 30℃ to 80℃. For example, the electrolysis voltage U1 can be 2.5V, 3V, 3.5V, 4V, or 4.5V, or any two of the above values; the electrolysis temperature T1 can be 30℃, 40℃, 50℃, 70℃, or 80℃, or any two of the above values. By controlling the electrolysis voltage and temperature within the above ranges, it is beneficial to ensure the full progress of the MeSO4 electrolysis reaction, generating sulfuric acid that can react with Li2CO3, thereby improving the lithium elution rate.

[0119] In some embodiments of this application, in step (1), the pretreatment includes crushing, sieving, and high-temperature treatment. The temperature T4 of the high-temperature treatment is 300°C to 800°C, the time t4 is 0.1h to 10h, and the atmosphere is selected from air or oxygen. For example, the temperature T4 of the high-temperature treatment can be 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C, or any two of the above numbers. For example, the time t4 of the high-temperature treatment can be 0.1h, 1h, 2h, 4h, 6h, 8h, or 10h, or any two of the above numbers. The positive current collector and the positive electrode material layer of the disassembled positive electrode are separated to obtain the positive electrode material. The positive electrode material is crushed and sieved to prepare positive electrode material powder within a certain particle size range. Subsequently, the positive electrode material powder is subjected to high-temperature treatment to remove the conductive agent, electrolyte, and binder, thereby obtaining black powder. This application does not have a particular limitation on the particle size of the positive electrode material powder, as long as it can achieve the purpose of this application.

[0120] Currently, the main method for recycling valuable metal elements from ternary lithium batteries is the wet process, which requires the use of large amounts of acids, alkalis, and extractants, and results in a low lithium recovery rate. Therefore, this application provides a method for extracting lithium from spent batteries to improve the lithium elution rate and thus increase the purity of lithium. Furthermore, this method eliminates the need for reducing agents and reduces the use of acid during the acid dissolution process.

[0121] This application provides a method for extracting lithium from waste batteries, which includes the following steps:

[0122] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0123] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0124] (3) Acid dissolution treatment: The calcined powder is reacted with sulfuric acid solution to obtain a solid-liquid mixture;

[0125] (4) First electrolysis treatment: The solid-liquid mixture is subjected to first electrolysis. After the first electrolysis is completed, the first filter residue and the first lithium-containing solution are obtained by filtration.

[0126] In some embodiments of this application, the above-mentioned method for extracting lithium further includes step (5), which is a purification process: the first lithium-containing solution is purified to obtain purified Li2SO4.

[0127] This application also provides a method for extracting lithium from waste batteries, which includes the following steps:

[0128] (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder;

[0129] (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder;

[0130] (3) Acid dissolution treatment: The calcined powder is reacted with sulfuric acid solution to obtain a solid-liquid mixture;

[0131] (4) First electrolysis treatment: The solid-liquid mixture is subjected to first electrolysis. After the first electrolysis is completed, the first filter residue and the first lithium-containing solution are obtained by filtration.

[0132] (5) Purification treatment: The first lithium-containing solution is purified to obtain purified Li2SO4.

[0133] In this application, ternary cathode material refers to ternary cathode material mainly composed of LiMeO2, wherein Me is selected from at least one of the elements Ni, Co, and Mn.

[0134] The method provided in this application can improve the purity of the obtained Li₂SO₄. Specifically, by reducing and roasting black powder with a reducing agent, the Me element in the black powder is converted into elemental Me and / or MeO, and the lithium element is converted into solid lithium carbonate. The roasted powder after reduction and roasting is then subjected to electrolytic lithium extraction. A slight excess of acid is used to dissolve the roasted powder, which not only reduces the amount of acid used but also eliminates the need for a reducing agent in the acid dissolution process. The dissolved nickel sulfate, cobalt sulfate, and manganese sulfate are subjected to a first electrolytic treatment. The acid generated in the first electrolytic treatment is used to dissolve the undissolved lithium carbonate from the previous step, improving the lithium elution rate and obtaining a solid powder and a first lithium-containing solution. The lithium elution rate of the first lithium-containing solution is ≥98%, and no additional acid is consumed during the first electrolytic treatment. The first lithium-containing solution contains Li₂SO₄ and trace amounts of MeSO₄. A second electrolytic treatment is then performed on the first lithium-containing solution to further purify lithium. Alternatively, the first lithium-containing solution can be further purified by organic solvent extraction or alkali precipitation. The second electrolytic treatment involves adjusting the solid content of the slurry using the calcined powder. This second electrolytic treatment yields small amounts of nickel-cobalt metal and manganese dioxide, resulting in a purified lithium sulfate solution with a purity exceeding 99%. Furthermore, this method significantly reduces the amount of sulfuric acid used compared to traditional processes, which often require SO4 in combination with Li, Co, Ni, and Mn. 2-If calculated using sulfur (S), 1 mol Li corresponds to 0.5 mol S, and 1 mol Co / Ni / Mn corresponds to 1 mol S. Therefore, the amount of S needed to match the molar amounts of Li, Co, Ni, and Mn is required. However, in this method, the H2SO4 generated during the electrolysis of CoSO4, NiSO4, and MnSO4 reacts with the undissolved Li. Overall, only the amount of S required for Li is needed. That is, in this process, the molar ratio of Li in the calcined powder to H in the sulfuric acid solution should be 1:(0.98~1.3), preferably 1:(1.01~1.1. This reduces the need for sulfuric acid or acidic substances and reducing agents, and also results in a high lithium elution rate.

[0135] In some embodiments of this application, step (2) of reducing and calcining the black powder includes: calcining the black powder with a reducing agent, the reducing agent including C and / or CO; and, in step (2), the calcined powder obtained includes Li2CO3 and Me-containing powder; wherein, the Me-containing powder includes elemental Me and / or MeO; and Me is selected from at least one of Ni, Co and Mn elements.

[0136] In some embodiments of this application, in step (2), the amount of reducing agent is 8 wt% to 15 wt% of the black powder; the reduction roasting temperature T3 is 550℃ to 700℃, and the roasting time t3 is 1h to 3h. For example, the amount of reducing agent can be 8 wt%, 10 wt%, 12 wt%, 13 wt%, or 15 wt% of the black powder, or any two of the above figures; the reduction roasting temperature T3 can be 550℃, 580℃, 620℃, 650℃, or 700℃, or any two of the above figures; the roasting time t3 can be 1h, 1.5h, 2h, 2.5h, or 3h, or any two of the above figures. By controlling the amount of reducing agent and the reduction roasting temperature and reaction time within the above ranges, the black powder can fully react with the reducing agent, converting the lithium element in the black powder into Li2CO3, and the Me element in the black powder into elemental Me and / or MeO, which is beneficial for subsequent acid dissolution treatment.

[0137] For example, when the reducing substance used in step (2) is C, the reaction equation is: 2LiMeO2+C=Li2CO3+Me+MeO.

[0138] When using carbon powder for reduction, an inert gas, such as N2, can be introduced.

[0139] For example, when the reducing substance used in step (2) is CO, the reaction equation is: 2LiMeO2+2CO=Li2CO3+Me+MeO+CO2.

[0140] In some embodiments of this application, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase, wherein the liquid phase contains Li2SO4 and MeSO4, and the solid phase contains Li2CO3 and Me-containing powder.

[0141] In some embodiments of this application, in step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3), preferably 1:(1.01~1.1). For example, the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution can be 1:0.98, 1:1.01, 1:1.02, 1:1.04, 1:1.07, 1:1.08, 1:1.1, 1:1.17, 1:1.25, or 1:1.3, or any two of the above numbers. By controlling the amount of sulfuric acid within the above range, most of the Li2CO3 in the calcined powder can be dissolved to generate Li2SO4. Li2SO4 enters the liquid phase of the solid-liquid mixture. At the same time, a small amount of elemental Me and / or MeO in the calcined powder will also react with sulfuric acid to generate MeSO4, which enters the liquid phase of the solid-liquid mixture. Acid dissolution yields a large amount of Li₂SO₄, a small amount of undissolved solid Li₂CO₃, a large amount of undissolved solid elemental Me and / or MeO, and a small amount of MeSO₄. The large amount of Li₂SO₄ and the small amount of MeSO₄ enter the liquid phase, while the small amount of undissolved solid Li₂CO₃ and the large amount of undissolved solid elemental Me and / or MeO remain in the solid phase. Through acid dissolution, not only can most of the Li₂SO₄ be dissolved... + The Li enters the liquid phase, while most of the Me-containing powder remains in the solid phase. + Separating Me-containing powders using both liquid and solid phases can yield high-purity Me-containing powders. These powders primarily include Ni, Co, and MnO, and Li... + It has a high elution rate in the liquid phase (around 88% to 92%) and fewer impurity phases in the liquid phase.

[0142] In this process, by reasonably controlling H + The amount or SO4 2- The amount of H + The amount of Li + A slight excess of the solution allows for the "stepwise" elution of Li. The first step involves acid washing (H+). + Most of the Li element was eluted from the solid phase and impregnated into the liquid phase. At the same time, the Me element also combined with some SO4. 2- Immersed in the liquid phase, controlling the portion of SO4 bound by Me element. 2-The molar amount of the first step corresponds to the uneluted Li₂CO₃ in the solid phase, preparing for the first electrolytic lithium washing step in the second step. The second step utilizes the electrolysis of MeSO₄ in the liquid phase to generate H₂SO₄. Since the molar amount of H₂SO₄ generated corresponds to the uneluted Li₂CO₃ in the solid phase, it can achieve the elution of as much Li₂CO₃ as possible from the remaining solid phase, while the Me element remains in the solid phase, i.e., the first filter residue. This two-step elution avoids acid waste and achieves a high overall elution rate (over 98%), while the Me element remains in the solid phase, thus achieving the separation of Li and Me elements.

[0143] If H + Excessive amounts will wash away more elemental Me and / or MeO, reducing the amount of Ni in the liquid phase. 2+ Co 2+ Increased content of certain elements affects the purity of Li₂SO₄, increasing the complexity of subsequent purification and also impacting the recovery rates of nickel, cobalt, and manganese. If H₂... + Too little, Li + The elution rate is low, which is not conducive to lithium recovery, and the Li in the Me-containing powder is also low. + The content will increase, but the purity will be lower, requiring further purification.

[0144] When the molar ratio of Li in the calcined powder to H in the sulfuric acid solution is 1:(1.01~1.1) during acid dissolution, the first lithium elution rate is between 88% and 92%, indicating that the appropriate Li content is achieved. + With H + The molar ratio, even if H + A slight excess can make Li + This allows for more thorough separation of Me-containing powders in both liquid and solid phases, further improving the purity of nickel-cobalt-manganese powders, primarily including Ni, Co, and MnO, and Li. + It has a higher elution rate in the liquid phase and fewer impurity phases in the liquid phase.

[0145] In this application, the first lithium elution rate after acid dissolution treatment is 88%–92%. Controlling this range not only achieves a high overall lithium elution rate but also improves the recovery rate and purity of Me. If the first lithium elution rate is too high, more acid will be used, resulting in more Me being eluted, wasting acid and reducing Me recovery, thus affecting Li₂SO₄ purity. If the first lithium elution rate is too low, more Li will remain in the solid phase, hindering Li recovery and reducing solid phase purity.

[0146] In this application, the concentration of sulfuric acid is not strictly required. The concentration of the sulfuric acid solution can be selected from 1 mol / L to 5 mol / L, and more specifically from 4.5 mol / L to 5.0 mol / L. For example, when using high-concentration sulfuric acid, greater than 5 mol / L, the concentration of sulfuric acid can be diluted with water to make the acid dissolution process easier; or sulfuric acid with a concentration of 1 mol / L to 5 mol / L can be used directly. Choosing sulfuric acid within this concentration range is beneficial for completing the acid dissolution process in a short time, and the acid dissolution reaction will also be more thorough.

[0147] In some embodiments of this application, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase. The liquid phase contains Li₂SO₄ and MeSO₄, and the solid phase contains Li₂CO₃ and Me-containing powder. In the liquid phase, the molar amount of Li in Li₂SO₄ is p1, and the molar amount of Me in MeSO₄ is p2, satisfying p1 > p2. In the solid phase, the molar amount of Me in the Me-containing powder is p3, and the molar amount of Li in Li₂CO₃ is p4, satisfying p3 > p4. The black powder mainly contains LiMeO₂, and the molar ratio of Li to Me is approximately 1:1. The ratio of the two remains unchanged in the calcined powder obtained after calcination. Sulfuric acid preferentially reacts with Li2CO3 in the calcined powder, and then with elemental Me and / or MeO in the calcined powder. Most of the Li2CO3 reacts with sulfuric acid to produce a large amount of Li2SO4, while a small amount of elemental Me and / or MeO also reacts with sulfuric acid to produce a small amount of MeSO4. A large amount of Li2SO4 and a small amount of MeSO4 enter the liquid phase, so p1 > p2 in the liquid phase. A small amount of undissolved solid Li2CO3 and a large amount of undissolved solid elemental Me and / or MeO remain in the solid phase, so p3 > p4 in the solid phase.

[0148] In some embodiments of this application, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%. After acid dissolution treatment, most of the Li2CO3 in the calcined powder reacts with sulfuric acid to generate Li2SO4. The generated Li2SO4 enters the liquid phase, that is, most of the lithium element in the calcined powder enters the liquid phase. The first lithium elution rate after acid dissolution treatment is 88% to 92%.

[0149] In this application, the acid dissolution treatment in step (3) includes the following reactions: Li2CO3 + H2SO4 = Li2SO4 + CO2↑ + H2O; Me + H2SO4 = H2↑ + MeSO4; MeO + H2SO4 = H2O + MeSO4

[0150] In some embodiments of this application, step (4), the first electrolysis of the solid-liquid mixture includes electrolyzing the MeSO4 in the liquid phase of the solid-liquid mixture. In some embodiments of this application, in step (4), the second lithium elution rate of the first lithium-containing solution is ≥98%.

[0151] In this application, when Me is selected from Ni, Co, and Mn (i.e., nickel-cobalt-manganese ternary batteries), the electrolysis of CoSO4 yields products including elemental Co and sulfuric acid, the electrolysis of NiSO4 yields products including elemental Ni and sulfuric acid, and the electrolysis of MnSO4 yields products including sulfuric acid containing MnO2. The proportions of nickel, cobalt, and manganese in MeSO4 are not limited in this application, but are generally similar to the proportions of nickel, cobalt, and manganese in the positive electrode active material. Exemplarily, the first electrolysis reaction is carried out in the following manner:

[0152] The electrolytic treatment in step (4) includes the following reactions:

[0153] Electrolysis of MeSO4 in the solid-liquid mixture produces sulfuric acid, allowing the remaining small amount of solid phase Li2CO3 to continue reacting with sulfuric acid to form Li2SO4 that can exist in the liquid phase. Therefore, the mass n1 of Li2SO4 in the first lithium-containing solution is greater than the mass m1 of Li2SO4 in the liquid phase of the solid-liquid mixture in step (3), thus improving the lithium elution rate. The second lithium elution rate of the first lithium-containing solution is ≥98%. This means maximizing the elution rate of Li... + In the liquid phase, nickel, cobalt, and manganese are separated in the solid phase, thus achieving the separation and purification of the two elements, namely Li and Me, where Me is Ni, Co, and Mn.

[0154] In some embodiments of this application, in step (4), the first filter residue includes Me-containing powder; the mass percentage of Me-containing powder in the first filter residue is w1%; satisfying: w1% > w2%; where w2% is the mass percentage of Me-containing powder in the solid phase of the solid-liquid mixture in step (3). In the above electrolytic treatment, since the Li2CO3 acid in the solid phase dissolves and leaches into the liquid phase, it is equivalent to purifying the solid phase. Therefore, the mass percentage of Me-containing powder in the first filter residue, w1%, is greater than the mass percentage of Me-containing powder in the solid phase of the solid-liquid mixture in step (3), w2%. That is, the sulfuric acid generated by the first electrolysis can react with the Li2CO3 in the solid phase, which is equivalent to purifying the solid phase, thus increasing the mass percentage of Me-containing powder in the first filter residue.

[0155] In some embodiments of this application, in step (4), the first electrolysis also yields an anode product and a cathode product; the anode product includes MnO2; the cathode product includes at least one of elemental Ni and elemental Co. Taking a nickel-cobalt-manganese ternary battery as an example, the above-mentioned first electrolysis yields the anode product MnO2 and the cathode products elemental Ni and elemental Co.

[0156] In some embodiments of this application, in step (4), the conditions for the end of the first electrolysis include: for every 100g of black powder, when the electrolysis capacity C1 in the first electrolysis process satisfies formula b, the first electrolysis ends; 10Ah≤C1≤13Ah Formula b.

[0157] By adjusting the electrolysis capacity C1 within the above range, the electrolysis of MeSO4 is achieved, thereby separating the original compounds with MeSO4. 2+ Combined SO4 2- , with Li + This combination improves the elution rate of lithium.

[0158] The Li elution rate during the acid dissolution process is related to the electrolytic capacity C1 of the subsequent electrolysis. In this application, the electrolytic capacity C1 during the electrolysis process can be determined based on the first Li elution rate during the acid dissolution process.

[0159] In some embodiments of this application, the conditions for ending electrolysis in step (4) include: for every 100g of the black powder, the first lithium elution rate after acid dissolution treatment in step (3) is 88% to 90%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula b1; 11Ah≤C1≤13Ah Formula b1.

[0160] In some embodiments of this application, the conditions for ending electrolysis in step (4) include: for every 100g of the black powder, the first lithium elution rate after acid dissolution treatment in step (3) is 90% to 92%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula b2; 10Ah≤C1≤12Ah Formula b2.

[0161] In some embodiments of this application, the voltage U1 of the first electrolysis is 2.5V to 4.5V, and the temperature T1 is 30℃ to 80℃. For example, the voltage U1 of the first electrolysis can be 2.5V, 3V, 3.5V, 4V, or 4.5V, or any two of the above values; the temperature T1 of the first electrolysis can be 30℃, 40℃, 50℃, 70℃, or 80℃, or any two of the above values. By controlling the voltage and temperature of the first electrolysis within the above ranges, it is beneficial to ensure the full progress of the first MeSO4 electrolysis reaction, generating sulfuric acid that can react with Li2CO3, thereby improving the lithium elution rate.

[0162] In some embodiments of this application, in step (5), the purification process is selected from any of the following:

[0163] Method 1: The purification process is a second electrolytic process, which includes the following steps: adding calcined powder to the first lithium-containing solution to obtain a slurry, performing a second electrolysis on the slurry, and after the second electrolysis is completed, filtering to obtain a second filter residue and a second lithium-containing solution. The second lithium-containing solution contains purified Li2SO4, and the slurry contains a solid phase and a liquid phase.

[0164] In some embodiments of this application, step (5) is a second electrolytic treatment, and the solid content of the slurry is 1 g / L to 100 g / L, preferably 5 g / L to 80 g / L. For example, the solid content of the slurry can be 1 g / L, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 22 g / L, 30 g / L, 34 g / L, 39 g / L, 45 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L, or between any two of the above figures. In some embodiments of this application, the liquid phase of the slurry contains Li2SO4 and MeSO4, and the solid phase contains calcined powder. In some embodiments of this application, the second electrolysis of the slurry includes: electrolyzing the MeSO4 in the liquid phase of the slurry. The second electrolytic treatment further purifies lithium. By adjusting the solid content of the slurry within the aforementioned range using calcined powder, trace amounts of MeSO4 in the first lithium-containing solution can be further electrolyzed, purifying Li2SO4. Specifically, calcined powder is first added to the first lithium-containing solution to obtain a slurry. The solid content of the slurry can be controlled by adjusting the amount of calcined powder added. Maintaining the solid content within the aforementioned range allows for the complete electrolysis of trace amounts of MeSO4 in the liquid phase of the slurry, generating sulfuric acid. The generated sulfuric acid further reacts with Li2CO3 in the added calcined powder to generate Li2SO4, which then enters the liquid phase of the slurry. This increases the Li2SO4 content in the liquid phase and decreases the MeSO4 content, achieving further lithium purification. This process also allows for trace lithium extraction using the added calcined powder.

[0165] In this application, since calcined powder is added to the first lithium-containing solution, during the preparation of the slurry, the calcined powder contains Li2CO3. When the calcined powder is added to the water system, a small amount of Li2CO3 may dissolve, making the pH of the system around 7, for example, pH 5 to 8.

[0166] In this application, when Me is selected from Ni, Co, and Mn (i.e., nickel-cobalt-manganese ternary batteries), the product obtained after electrolysis of CoSO4 includes elemental Co and sulfuric acid, the product obtained after electrolysis of NiSO4 includes elemental Ni and sulfuric acid, and the product obtained after electrolysis of MnSO4 includes sulfuric acid containing MnO2. The proportions of nickel, cobalt, and manganese in the first lithium-containing solution are not limited in this application. Exemplarily, the second electrolysis process includes the following reactions: Li2CO3+H2SO4=Li2SO4+CO2↑+H2O.

[0167] Specifically, adding calcined powder during the second electrolysis process can adjust the solid content of the slurry to between 1 g / L and 100 g / L, ensuring a more thorough second electrolysis, improving the purity of Li₂SO₄, and also allowing for the extraction of a small amount of lithium from the added calcined powder, even if the Li₂CO₃ in the calcined powder is converted into Li₂SO₄. When the solid content is less than 1 g / L, the solid content is too low, resulting in a low Li₂CO₃ content in the slurry, which leads to insufficient SO₄ produced during electrolysis. 2- >2Li + There will be SO4 2- The remainder, and Me 2+ The combination of NiSO4, CoSO4, and MnSO4 reduces the purity of Li2SO4. When the solid content exceeds 100 g / L, the slurry becomes too viscous, hindering effective electrolysis. Preferably, the solid content of the slurry is between 5 g / L and 80 g / L. A solid content below 5 g / L results in a smaller throughput and lower efficiency; a solid content above 80 g / L causes the slurry to gradually become viscous, leading to a gradual decrease in electrolysis efficiency.

[0168] In some embodiments of this application, step (5) is a second electrolysis process, the second lithium-containing solution includes Li2SO4, and the mass of Li2SO4 in the second lithium-containing solution is s1; in step (4), the first lithium-containing solution includes Li2SO4 and MeSO4, and the mass of Li2SO4 in the first lithium-containing solution is n1; satisfying s1 > n1 > m1, where m1 is the mass of Li2SO4 in the solid-liquid mixture of step (3). In some embodiments of this application, the purity of Li2SO4 obtained after purification is ≥99%. In some embodiments of this application, in step (4), the second lithium elution rate of the first lithium-containing solution is ≥98%.

[0169] By adding calcined powder to the first lithium-containing solution, the trace amount of MeSO4 in the first lithium-containing solution is further electrolyzed to generate sulfuric acid, which converts the Li2CO3 in the newly added calcined powder into Li2SO4. Therefore, the mass s1 of Li2SO4 in the second lithium-containing solution is greater than the mass n1 of Li2SO4 in the first lithium-containing solution, thus improving the purity of the Li2SO4 obtained in the solution. After purification, the purity of the Li2SO4 obtained is ≥99%. In step (4) above, by electrolyzing MeSO4 in the solid-liquid mixture to generate sulfuric acid, the remaining small amount of solid phase Li2CO3 can continue to react with sulfuric acid to form Li2SO4 that can exist in the liquid phase. Therefore, the mass n1 of Li2SO4 in the first lithium-containing solution is greater than the mass m1 of Li2SO4 in the solid-liquid mixture in step (3), thus improving the lithium elution rate. The second lithium elution rate of the first lithium-containing solution is ≥98%.

[0170] In some embodiments of this application, step (5) is a second electrolysis process, which further yields an anode product and a cathode product; the anode product includes MnO2; the cathode product includes at least one of elemental Ni and elemental Co. Taking a nickel-cobalt-manganese ternary battery as an example, the above-mentioned second electrolysis yields the anode product MnO2 and the cathode products elemental Ni and elemental Co.

[0171] In some embodiments of this application, the conditions for the termination of the second electrolysis include: for every 100g of black powder, the second electrolysis terminates when the electrolysis capacity C2 in the second electrolysis process satisfies formula a;

[0172] Wherein, C1 represents the electrolytic capacity per 100g of black powder during the first electrolysis process; the value range of C1 is: 10Ah ≤ C1. For example, the electrolytic capacity C1 during the electrolysis process can be determined based on the first Li elution rate during the acid dissolution process. By adjusting the second electrolytic capacity C2 within the above range, the trace amount of MeSO4 in the first content solution is electrolyzed, thus removing the original Me... 2+ Combined SO4 2- , with Li + This combination improves the purity of lithium.

[0173] In some embodiments of this application, step (5) is a second electrolysis process, wherein the voltage U2 of the second electrolysis is 2.5V to 4.5V and the temperature T2 is 30℃ to 80℃. For example, the voltage U2 of the second electrolysis can be 2.5V, 3V, 3.5V, 4V or 4.5V, or any two of the above numbers; the temperature T2 of the second electrolysis can be 30℃, 40℃, 50℃, 70℃ or 80℃, or any two of the above numbers. By controlling the voltage and temperature of the second electrolysis within the above ranges, it is beneficial to ensure the full progress of the second electrolysis reaction, so that the MeSO4 in the liquid phase of the slurry is electrolyzed to generate sulfuric acid that can react with Li2CO3, the content of MeSO4 in the liquid phase of the slurry decreases, and the generated sulfuric acid further reacts with the Li2CO3 in the calcined powder in the solid phase of the slurry to generate Li2SO4. The Li2SO4 enters the liquid phase of the slurry, the content of LiSO4 in the liquid phase of the slurry increases, and the purity of the obtained Li2SO4 is improved.

[0174] In this application, the pH of the second electrolysis process is 5 to 6.

[0175] The purification method described in this application can also be any other suitable method in the prior art. For example, extraction using organic solvents or precipitation by adding alkali, etc. Examples are described below:

[0176] Method 2: Organic solvent extraction, which includes the following steps:

[0177] The first lithium-containing solution, which contains Li₂SO₄ and trace amounts of MeSO₄, is purged with oxygen to remove Mn. 2+ The solution is oxidized to manganese dioxide, filtered to obtain manganese dioxide and a nickel-cobalt-containing solution. The pH of the nickel-cobalt-containing solution is then adjusted to 3-4 by adding acid, which can be at least one of HCl and H₂SO₄. An extractant is then added to extract nickel and cobalt ions. The extractant is a mixture of nickel extractant HBL110 and kerosene at a volume ratio of 0.15:1, with a volume ratio of extractant to nickel-cobalt-containing solution of 0.5:1. The extraction equilibrium pH is 4. The extract containing nickel and cobalt ions is back-extracted with 2 mol / L to 6 mol / L sulfuric acid to obtain a high-purity mixed solution of nickel sulfate and cobalt sulfate. The raffinate contains purified lithium sulfate.

[0178] Method 3: Alkali precipitation. Alkali precipitation includes the following steps: adding alkali to the obtained first lithium-containing solution to adjust the pH of the first lithium-containing solution to 10-11. The alkali can be at least one of NaOH, KOH, or ammonia water. A pure lithium sulfate solution can be obtained by completely precipitating nickel hydroxide, cobalt hydroxide, and manganese hydroxide.

[0179] The purity of lithium can be improved by further purifying the first lithium-containing solution using the three methods described above.

[0180] In some embodiments of this application, in step (1), the pretreatment includes crushing, sieving, and high-temperature treatment. The temperature T4 of the high-temperature treatment is 300°C to 800°C, the time t4 is 0.1h to 10h, and the atmosphere is selected from air or oxygen. For example, the temperature T4 of the high-temperature treatment can be 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C, or any two of the above numbers. For example, the time t4 of the high-temperature treatment can be 0.1h, 1h, 2h, 4h, 6h, 8h, or 10h, or any two of the above numbers. The positive current collector and the positive electrode material layer of the disassembled positive electrode are separated to obtain the positive electrode material. The positive electrode material is crushed and sieved to prepare positive electrode material powder within a certain particle size range. Subsequently, the positive electrode material powder is subjected to high-temperature treatment to remove the conductive agent, electrolyte, and binder, thereby obtaining black powder. This application does not have a particular limitation on the particle size of the positive electrode material powder, as long as it can achieve the purpose of this application.

[0181] Example

[0182] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0183] Test methods and equipment:

[0184] Calculation of lithium elution rate:

[0185] The mass percentage (%) of Li in black powder, the mass concentration (mg / kg) of Li in the liquid phase of the solid-liquid mixture, and the mass concentration (mg / kg) of Li in the filter residue were determined by ICP.

[0186] The Li content (in g) in the solid phase of a solid-liquid mixture = the Li mass concentration (in mg / kg) in the solid phase of the solid-liquid mixture × 10 -6 × The mass of the solid phase in the solid-liquid mixture (in g).

[0187] Li content in the first filter residue (in g) = Li mass concentration in the first filter residue (in mg / kg) × 10 -6 × The mass of the first filter residue (in grams).

[0188] Li content in black powder (in g) = mass percentage of Li in black powder × mass of black powder (in g).

[0189] First lithium elution rate = (1 - Li content in the solid phase of the solid-liquid mixture / Li content in the black powder) × 100%.

[0190] Second lithium elution rate = (1 - Li content in filter residue / Li content in black powder) × 100%.

[0191] Filter residue purity test:

[0192] The content of elemental Me and / or MeO in the filter residue was determined by ICP, in mg / kg.

[0193] Filter residue purity = content of elemental substances and / or MeO in the filter residue × 10 -6 ×100%.

[0194] Purity test of Li2SO4:

[0195] The content of Li₂SO₄ obtained after purification was determined by ICP, in mg / L. The purity of Li₂SO₄ = (lithium concentration in the second lithium-containing solution / (impurity concentration in the second lithium-containing solution + lithium concentration in the second lithium-containing solution)) × 100%.

[0196] Preparation of black powder:

[0197] Used ternary 811 lithium-ion batteries (LiNi) 0.8 Co 0.1 Mn 0.1The positive electrode material layer obtained from the disassembly (O2) is crushed and sieved to obtain positive electrode material powder. The positive electrode material powder is then pretreated in a rotary kiln at T4 = 550℃ by introducing air to remove residual conductive agent, electrolyte, and binder. The pretreatment time is t4 = 2 hours. The powder is then passed through a 150-mesh sieve to obtain black powder A, where the lithium content is calculated to be 6.9 wt%.

[0198] Used ternary 111 lithium-ion batteries (LiNi) 1 / 3 Co 1 / 3 Mn 1 / 3 The positive electrode material layer obtained from the disassembly (O2) is crushed and sieved to obtain positive electrode material powder. The positive electrode material powder is then pretreated in a rotary kiln at T4 = 550℃ by introducing air to remove residual conductive agent, electrolyte, and binder. The pretreatment time is t4 = 2 hours. The powder is then passed through a 150-mesh sieve to obtain black powder B, where the lithium content of black powder B is calculated to be 7.1 wt%.

[0199] Example 1-1

[0200] Figure 1 is a flowchart of the experiment in Example 1-1. The specific steps are as follows:

[0201] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃ for a duration t1 of 90 minutes, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 111.3ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.07, resulting in a solid-liquid mixture with approximately 51g of solid phase. At this point, the first lithium elution rate was 90.6%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and an electrolysis capacity C1 of 11Ah. After electrolysis, the mixture was filtered. The filter residue was approximately 50g of nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.2%. The filtrate was a lithium-containing solution with a second lithium elution rate of 98%.

[0202] Table 1-1 Mass concentration of each element in the solid phase of a solid-liquid mixture

[0203] Table 1-2 Mass concentration of various elements in the powder and filter residue after electrolysis

[0204] Examples 1-2

[0205] 100g of black powder A, mixed with 12g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 600℃ for a duration t1 of 150min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 116.6ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.1, resulting in a first lithium elution rate of 92%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.8V, a temperature T1 of 60℃, and an electrolysis capacity C1 of 10.2Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (Co, Ni, MnO) powder with a purity of 98.7%, and the filtrate was a lithium-containing solution with a second lithium elution rate of 98.5%.

[0206] Examples 1-3

[0207] 100g of black powder A, mixed with 15g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 550℃, and the duration t1 was 180min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 112.4ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.08, resulting in a first lithium elution rate of 91%. After acid dissolution, electrolysis was performed using a constant voltage electrolysis method (U1 = 3V), a temperature T1 of 50℃, and an electrolysis capacity C1 of 10.8Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (Co, Ni, MnO) powder with a purity of 98.3%, and the filtrate was a lithium-containing solution. The second lithium elution rate of the lithium-containing solution was 98.4%.

[0208] Examples 1-4

[0209] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 680℃ for a duration t1 of 120min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 106.2ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.02, resulting in a first lithium elution rate of 89.1%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and an electrolysis capacity C1 of 12.1Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.5%. The filtrate was a lithium-containing solution, with a second lithium elution rate of 98.2%.

[0210] Examples 1-5

[0211] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 137.8ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.3, resulting in a first lithium elution rate of 95%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and an electrolysis capacity C1 of 15Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 99.3%, and the filtrate was a lithium-containing solution with a second lithium elution rate of 99.3%.

[0212] In this embodiment, due to the addition of more acid, more nickel, cobalt, and manganese elements were washed off after acid washing (i.e., nickel, cobalt, and manganese elements entered the liquid phase). Compared with Example 1-1, the content of nickel, cobalt, and manganese elements in the liquid phase was about 2 to 3 times, which reduced the purity of lithium sulfate in the lithium-containing solution, which was not conducive to the subsequent purification of lithium sulfate, and the recovery rate of nickel, cobalt, and manganese was low.

[0213] Examples 1-6

[0214] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃ for a duration t1 of 90 minutes, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 103.9ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:0.98, resulting in a first lithium elution rate of 85%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and an electrolysis capacity C1 of 13.8Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 97.6%. The filtrate was a lithium-containing solution, with a second lithium elution rate of 94.9%.

[0215] Examples 1-7

[0216] 100g of black powder B, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃ for a duration t1 of 90 minutes, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 111.3ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.04, resulting in a first lithium elution rate of 91.1%. After acid dissolution, electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and an electrolysis capacity C1 of 11.3Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.7%, and the filtrate was a lithium-containing solution. The second lithium elution rate of the lithium-containing solution was 98.1%.

[0217] Comparative Example 1-1

[0218] 100g of black powder mixed with 10g of carbon was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 99ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:0.95, resulting in a first lithium elution rate of 80%. After acid dissolution, electrolysis was performed using a constant voltage electrolysis method (U1 = 3.5V), a temperature T1 of 50℃, and an electrolysis capacity C1 of 14Ah. After electrolysis, the mixture was filtered. The filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 85%. The filtrate was a lithium-containing solution, with a second lithium elution rate of 84.1%. The nickel-cobalt-manganese powder contained numerous impurities.

[0219] Example 2-1

[0220] Figure 2 is a flowchart of the experiment in Example 2-1. The specific steps are as follows:

[0221] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 111.3ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.07, resulting in a solid-liquid mixture with approximately 51g of solid phase. At this point, the first lithium elution rate was 90.6%. After acid dissolution, the first electrolysis is carried out. The first electrolysis adopts constant voltage electrolysis of U1 = 3.5V, temperature T1 is 50℃, and the first electrolysis capacity C1 is 11Ah. After the first electrolysis is completed, the filter is filtered. The first filter residue is nickel cobalt manganese (containing Co, Ni, MnO) powder, with a mass of about 50g and a purity of 98.2%. The filtrate is the first lithium-containing solution, and the second lithium elution rate of the first lithium-containing solution is 98%.

[0222] The first lithium-containing solution was mixed with 10g of fresh calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 15g / L. The second electrolysis capacity C2 was set to 3Ah, the temperature T2 to 50℃, the voltage U2 to 3.5V, and the pH to approximately 5.6. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.95%. The second filter residue underwent the aforementioned acid dissolution treatment and the first electrolysis treatment, achieving process recycling.

[0223] Table 2-1 Mass concentration of each element in the solid phase of a solid-liquid mixture

[0224] Table 2-2 Mass concentration of each element in the powder (i.e., the first filter residue) after the first electrolysis.

[0225] Table 2-3 Concentrations of various elements in the lithium sulfate solution (i.e., the second lithium-containing solution) after the second electrolysis.

[0226] Example 2-2

[0227] 100g of black powder A, mixed with 12g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating began. The tube furnace temperature T3 was set at 600℃ for a duration t1 of 150min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 116.6ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.1, resulting in a first lithium elution rate of 92%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.8V, a temperature T1 of 60℃, and a first electrolysis capacity C1 of 10.2Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.7%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.5%.

[0228] The first lithium-containing solution was mixed with 20g of freshly calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 20g / L. The second electrolysis capacity C2 was set to 2.6Ah, temperature T2 to 80℃, voltage U2 to 3.5V, and pH to approximately 5.5. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.98%. The second filter residue underwent the aforementioned acid dissolution treatment and the first electrolysis treatment, achieving process recycling.

[0229] Example 2-3

[0230] 100g of black powder A, mixed with 15g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 550℃, and the duration t1 was 180min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 112.4ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.08, resulting in a first lithium elution rate of 91%. After acid dissolution, a first electrolysis was performed using a constant voltage electrolysis method (U1 = 3V), a temperature T1 of 50℃, and a first electrolysis capacity C1 of 10.8Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.3%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.4%.

[0231] The first lithium-containing solution was mixed with fresh calcined powder, with 30g of calcined powder used. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 50g / L. The second electrolysis capacity C2 was set to 3.2Ah, the temperature T2 to 50℃, the voltage U2 to 3.5V, and the pH to approximately 5.4. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.91%. The second filter residue underwent the above-mentioned acid dissolution treatment and first electrolysis treatment to achieve recycling in the process.

[0232] Examples 2-4

[0233] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 680℃ for a duration t1 of 120min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 106.2ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.02, resulting in a first lithium elution rate of 89.1%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and a first electrolysis capacity C1 of 12.1Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.5%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.2%.

[0234] The first lithium-containing solution was mixed with fresh calcined powder, with 5g of calcined powder used. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 5g / L. The second electrolysis capacity C2 was set to 5Ah, the temperature T2 to 50℃, the voltage U2 to 3.5V, and the pH to approximately 5.6. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.92%. The second filter residue underwent the above-mentioned acid dissolution treatment and first electrolysis treatment to achieve recycling in the process.

[0235] Examples 2-5

[0236] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 137.8ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.3, resulting in a first lithium elution rate of 95%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and a first electrolysis capacity C1 of 15Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 99.3%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 99.3%.

[0237] In this embodiment, due to the addition of more acid, more nickel, cobalt, and manganese elements were washed off after acid dissolution. That is, more nickel, cobalt, and manganese elements entered the liquid phase of the solid-liquid mixture. Compared with Example 2-1, the mass percentage of nickel, cobalt, and manganese elements in the liquid phase was about 2 to 3 times, which reduced the purity of lithium sulfate in the first lithium-containing solution, which was not conducive to the subsequent purification of lithium sulfate, and the recovery rate of nickel, cobalt, and manganese was low.

[0238] The first lithium-containing filtrate was mixed with new calcined powder, using 50g of black powder. Due to the high nickel, cobalt, and manganese content in the liquid phase, a larger amount of black powder was used. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 100g / L. The second electrolysis capacity C2 was set to 4Ah. During electrolysis, the temperature T2 was 50℃, the voltage U2 was 3.5V, and the pH was approximately 5.3. The solution was relatively viscous during electrolysis, resulting in low electrolysis efficiency.

[0239] Examples 2-6

[0240] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 103.9ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:0.98, resulting in a first lithium elution rate of 85%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and a first electrolysis capacity C1 of 13.8Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 97.6%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 94.9%.

[0241] The first lithium-containing solution was mixed with 10g of fresh calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 15g / L. The second electrolysis capacity C2 was set to 5Ah, the temperature T2 to 50℃, the voltage U2 to 3.5V, and the pH to approximately 5.6. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.93%. The second filter residue underwent the aforementioned acid dissolution treatment and the first electrolysis treatment, achieving process recycling.

[0242] Examples 2-7

[0243] 100g of black powder B, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 111.3ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.04, resulting in a first lithium elution rate of 91.1%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and a first electrolysis capacity C1 of 11.3Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.7%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.1%.

[0244] The first lithium-containing solution was mixed with 10g of fresh calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 30g / L. The second electrolysis capacity C2 was set to 4.5Ah, temperature T2 to 50℃, voltage U2 to 3.5V, and pH to approximately 5.4. After the second electrolysis, the mixture was filtered to obtain a second lithium-containing filtrate and a second filter residue. The purity of Li2SO4 in the second lithium-containing solution was 99.1%. The second filter residue underwent further acid dissolution and the first electrolysis treatment, achieving process recycling.

[0245] Comparative Example 2-1

[0246] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 700℃, and the duration t1 was 90min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 99ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:0.95, resulting in a first lithium elution rate of 80%. After acid dissolution, a first electrolysis was performed using a constant voltage electrolysis method (U1 = 3.5V), a temperature T1 of 50℃, and a first electrolysis capacity C1 of 14Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 85%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 84.1%. The nickel-cobalt-manganese powder contained numerous impurities.

[0247] The second lithium elution rate was low at 84.1%, so subsequent purification experiments were suspended.

[0248] Comparative Example 2-2 (The first electrolysis process is the same as in Example 2-3)

[0249] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 550℃, and the duration t1 was 180min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 112.4ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.08, resulting in a first lithium elution rate of 91%. After acid dissolution, a first electrolysis was performed using a constant voltage electrolysis method (U1 = 3V), a temperature T1 of 50℃, and a first electrolysis capacity C1 of 10.8Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.3%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.4%.

[0250] The first lithium-containing solution was mixed with 80g of new calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 200g / L. The second electrolysis capacity C2 was set to 4Ah, the temperature T2 to 50℃, the voltage U2 to 3.5V, and the pH to approximately 5.3. During the electrolysis process, the slurry became very viscous and could not be electrolyzed.

[0251] Comparative Examples 2-3 (The first electrolysis process is the same as in Examples 2-4)

[0252] 100g of black powder A, mixed with 10g of carbon, was used for reduction roasting. Nitrogen gas was first introduced to purge other gases from the tube, then heating was started. The tube furnace temperature T3 was set at 680℃ for a duration t1 of 120min, yielding roasted powder. After cooling, the roasted powder was removed and acid-dissolved using 106.2ml of 4.8mol / L sulfuric acid. The molar ratio of Li in the roasted powder to H in the sulfuric acid was approximately 1:1.02, resulting in a first lithium elution rate of 89.1%. After acid dissolution, a first electrolysis was performed at a constant voltage of U1 = 3.5V, a temperature T1 of 50℃, and a first electrolysis capacity C1 of 12.1Ah. After the first electrolysis, the mixture was filtered. The first filter residue was nickel-cobalt-manganese (containing Co, Ni, and MnO) powder with a purity of 98.5%. The filtrate was the first lithium-containing solution, with a second lithium elution rate of 98.2%.

[0253] The first lithium-containing solution was mixed with 1g of freshly calcined powder. After mixing, a second electrolysis was performed. Water was added to prepare a slurry with a solid content of 0.5g / L. The second electrolysis capacity C2 was set to 3Ah, temperature T2 to 50℃, voltage U2 to 3.5V, and pH to approximately 5.5. At the start of electrolysis, bubbles were observed forming on the cathode plate. After a period of time, significant bubbles appeared on the cathode plate, and the pH decreased by approximately 2. This was because the slurry contained too little calcined powder and too much acid, which could not neutralize the sulfuric acid produced in the second electrolysis, preventing the second electrolysis from proceeding normally and leading to the production of hydrogen gas.

[0254] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0255] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for extracting lithium from waste batteries, comprising the following steps: (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder; (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder; (3) Acid dissolution treatment: The calcined powder is reacted with sulfuric acid solution to obtain a solid-liquid mixture; (4) First electrolysis treatment: The solid-liquid mixture is subjected to first electrolysis. After the first electrolysis is completed, the first filter residue and the first lithium-containing solution are obtained by filtration.

2. The method according to claim 1, comprising the following steps: (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder; (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder; (3) Acid dissolution treatment: The calcined powder is subjected to acid dissolution reaction with sulfuric acid solution to obtain a solid-liquid mixture; the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3); (4) Electrolysis treatment: The solid-liquid mixture is electrolyzed. After the electrolysis is completed, the mixture is filtered to obtain filter residue and lithium-containing solution. The electrolysis is the first electrolysis, the filter residue is the first filter residue, and the lithium-containing solution is the first lithium-containing solution.

3. The method according to claim 2, wherein, In step (2), the reduction roasting of the black powder includes: The black powder is calcined in the presence of a reducing agent, wherein the reducing agent includes C and / or CO; and, In step (2), the calcined powder obtained includes Li2CO3 and Me-containing powder; The Me-containing powder includes elemental Me and / or MeO; The Me is selected from at least one of the elements Ni, Co, and Mn.

4. The method according to claim 2, wherein, In step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(1.01~1.1); Preferably, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase, wherein the liquid phase contains Li2SO4 and MeSO4, and the solid phase contains Li2CO3 and Me-containing powder.

5. The method according to claim 4, wherein, In step (3), in the liquid phase, the molar amount of Li in Li2SO4 is p1, and the molar amount of Me in MeSO4 is p2, satisfying p1 > p2; in the solid phase, the molar amount of Me in the Me-containing powder is p3, and the molar amount of Li in Li2CO3 is p4, satisfying p3 > p4. Preferably, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%.

6. The method according to claim 4, wherein, In step (4), the electrolysis of the solid-liquid mixture includes: The MeSO4 in the liquid phase of the solid-liquid mixture is electrolyzed.

7. The method according to claim 6, wherein, In step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, when the electrolysis capacity C1 in the electrolysis process satisfies Equation 1, the electrolysis ends; 10Ah≤C1 Equation 1.

8. The method according to claim 7, wherein, In step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, the first lithium elution rate after the acid dissolution treatment in step (3) is 88% to 90%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-a; 11Ah≤C1≤13Ah Formula 1-a.

9. The method according to claim 7, wherein, In step (4), the conditions for the end of electrolysis include: for every 100g of the black powder, the first lithium elution rate after the acid dissolution treatment in step (3) is 90% to 92%, and the electrolysis ends when the electrolysis capacity C1 in the electrolysis process satisfies formula 1-b; 10Ah≤C1≤12Ah Formula 1-b.

10. The method according to claim 6, wherein, In step (4), the lithium-containing solution includes Li2SO4; in the lithium-containing solution, the mass of the Li2SO4 is n1, satisfying n1 > m1, where m1 is the mass of the Li2SO4 in the liquid phase of the solid-liquid mixture in step (3); Preferably, in step (4), the second lithium elution rate of the lithium-containing solution is ≥98%; Preferably, in step (4), the filter residue includes the Me-containing powder; the mass percentage of the Me-containing powder in the filter residue is w1%; satisfying: w1% > w2%; wherein, w2% is the mass percentage of the Me-containing powder in the solid phase of the solid-liquid mixture in step (3); Preferably, in step (4), the electrolysis also yields an anode product and a cathode product; the anode product includes MnO2; the cathode product includes at least one of elemental Ni and elemental Co.

11. The method according to claim 2, wherein, At least one of the following conditions must be met: Condition a: In step (2), the amount of the reducing substance used is 8 wt% to 15 wt% of the black powder; Condition b: In step (2), the reduction calcination temperature T3 is 550℃~700℃, and the calcination time t3 is 1h~3h; Condition c: In step (3), the concentration of the sulfuric acid solution is 1 mol / L to 5 mol / L; Condition d: In step (4), the voltage U1 of the electrolysis is 2.5V to 4.5V and the temperature T1 is 30℃ to 80℃.

12. The method according to claim 1, comprising the following steps: (1) Pretreatment: Obtain waste ternary cathode material, and pretreat the waste ternary cathode material to obtain black powder; (2) Reduction roasting treatment: The black powder is reduced and roasted to obtain roasted powder; (3) Acid dissolution treatment: The calcined powder is subjected to acid dissolution reaction with sulfuric acid solution to obtain a solid-liquid mixture; (4) First electrolysis treatment: The solid-liquid mixture is subjected to a first electrolysis. After the first electrolysis is completed, the mixture is filtered to obtain a first filter residue and a first lithium-containing solution. (5) Purification treatment: The first lithium-containing solution is purified to obtain purified Li2SO4.

13. The method according to claim 12, wherein, In step (5), the purification process is selected from any of the following methods: Method 1: The purification process is a second electrolytic process, which includes the following steps: The calcined powder is added to the first lithium-containing solution to obtain a slurry. The slurry is then subjected to a second electrolysis. After the second electrolysis is completed, the slurry is filtered to obtain a second filter residue and a second lithium-containing solution. The second lithium-containing solution contains the purified Li2SO4. The slurry contains a solid phase and a liquid phase. Method 2: Organic solvent extraction; Method 3: Add alkali to precipitate.

14. The method according to claim 13, wherein, Step (5) is the first method, wherein the solid content of the slurry is 1 g / L to 100 g / L; preferably, the solid content of the slurry is 5 g / L to 80 g / L. Preferably, step (5) is the first method, wherein the liquid phase of the slurry contains Li2SO4 and MeSO4, and the solid phase contains the calcined powder; Preferably, step (5) is the first method, and the second electrolysis of the slurry includes: electrolyzing the MeSO4 in the liquid phase of the slurry.

15. The method according to claim 13, wherein, Step (5) is the first method, and the conditions for the end of the second electrolysis include: for every 100g of the black powder, when the electrolysis capacity C2 in the second electrolysis process satisfies formula a, the second electrolysis ends; Wherein, C1 is the electrolytic capacity for every 100g of the black powder during the first electrolysis process; The range of C1 is: 10Ah≤C1.

16. The method according to claim 13, wherein, Step (5) is the first method, where the second lithium-containing solution includes Li2SO4, and the mass of Li2SO4 in the second lithium-containing solution is s1; In step (4), the first lithium-containing solution includes Li2SO4 and MeSO4, and the mass of Li2SO4 in the first lithium-containing solution is n1; satisfying s1 > n1 > m1. Where m1 is the mass of Li2SO4 in the liquid phase of the solid-liquid mixture in step (3).

17. The method according to claim 12, wherein, In step (2), the reduction roasting of the black powder includes: The black powder is calcined in the presence of a reducing agent, wherein the reducing agent includes C and / or CO; and, In step (2), the calcined powder obtained includes Li2CO3 and Me-containing powder; The Me-containing powder includes elemental Me and / or MeO; The Me is selected from at least one of the elements Ni, Co, and Mn.

18. The method according to claim 12, wherein, In step (3), the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(0.98~1.3); preferably, the molar ratio of Li element in the calcined powder to H element in the sulfuric acid solution is 1:(1.01~1.1). Preferably, in step (3), the solid-liquid mixture comprises a liquid phase and a solid phase, wherein the liquid phase contains Li2SO4 and MeSO4, and the solid phase contains Li2CO3 and Me-containing powder; Preferably, in step (3), in the liquid phase, the molar amount of Li in Li2SO4 is p1, and the molar amount of Me in MeSO4 is p2, satisfying p1 > p2; in the solid phase, the molar amount of Me in the Me-containing powder is p3, and the molar amount of Li in Li2CO3 is p4, satisfying p3 > p4. Preferably, in step (3), the first lithium elution rate after acid dissolution treatment is 88% to 92%.

19. The method according to claim 18, wherein, In step (4), the first electrolysis of the solid-liquid mixture includes: electrolyzing the MeSO4 in the liquid phase of the solid-liquid mixture; Preferably, in step (4), the conditions for the first electrolysis to end include: for every 100g of the black powder, the first electrolysis ends when C1 satisfies formula b; 10Ah≤C1≤13Ah formula b; Preferably, in step (4), the elution rate of the second lithium in the first lithium-containing solution is ≥98%; Preferably, in step (4), the first filter residue includes the Me-containing powder, and the mass percentage of the Me-containing powder in the first filter residue is w1%; satisfying w1% > w2%, wherein w2% is the mass percentage of the Me-containing powder in the solid phase in the solid-liquid mixture of step (3).

20. The method according to claim 13, wherein, In steps (4) and (5), the first electrolysis process also yields a first anode product and a first cathode product, and the second electrolysis process also yields a second anode product and a second cathode product. The first anode product and the second anode product each independently comprise MnO2; The first cathode product and the second cathode product each independently include at least one of elemental Ni and elemental Co.

21. The method according to claim 12, wherein, At least one of the following conditions must be met: Condition a: In step (2), the amount of the reducing substance used is 8 wt% to 15 wt% of the black powder; Condition b: In step (2), the reduction calcination temperature T3 is 550℃~700℃, and the calcination time t3 is 1h~3h; Condition c: In step (3), the concentration of the sulfuric acid solution is 1 mol / L to 5 mol / L; Condition d: In step (4), the voltage U1 of the first electrolysis is 2.5V to 4.5V and the temperature T1 is 30℃ to 80℃; Condition e: In step (5), the voltage U2 of the second electrolysis is 2.5V to 4.5V and the temperature T2 is 30℃ to 80℃.

22. The method according to claim 12, wherein, The purity of the Li2SO4 obtained after purification is ≥99%.

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